/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

// Contributors: Christopher Williams
//               Mathias Bogaert
package org.apache.log4j;

import org.apache.log4j.helpers.DateLayout;
import org.apache.log4j.spi.LoggingEvent;

/**
 * TTCC layout format consists of time, thread, category and nested diagnostic
 * context information, hence the name.
 * 
 * <p>
 * Each of the four fields can be individually enabled or disabled. The time
 * format depends on the <code>DateFormat</code> used.
 * 
 * <p>
 * Here is an example TTCCLayout output with the
 * {@link org.apache.log4j.helpers.RelativeTimeDateFormat}.
 * 
 * <pre>
 * 176 [main] INFO  org.apache.log4j.examples.Sort - Populating an array of 2 elements in reverse order.
 * 225 [main] INFO  org.apache.log4j.examples.SortAlgo - Entered the sort method.
 * 262 [main] DEBUG org.apache.log4j.examples.SortAlgo.OUTER i=1 - Outer loop.
 * 276 [main] DEBUG org.apache.log4j.examples.SortAlgo.SWAP i=1 j=0 - Swapping intArray[0] = 1 and intArray[1] = 0
 * 290 [main] DEBUG org.apache.log4j.examples.SortAlgo.OUTER i=0 - Outer loop.
 * 304 [main] INFO  org.apache.log4j.examples.SortAlgo.DUMP - Dump of interger array:
 * 317 [main] INFO  org.apache.log4j.examples.SortAlgo.DUMP - Element [0] = 0
 * 331 [main] INFO  org.apache.log4j.examples.SortAlgo.DUMP - Element [1] = 1
 * 343 [main] INFO  org.apache.log4j.examples.Sort - The next log statement should be an error message.
 * 346 [main] ERROR org.apache.log4j.examples.SortAlgo.DUMP - Tried to dump an uninitialized array.
 *         at org.apache.log4j.examples.SortAlgo.dump(SortAlgo.java:58)
 *         at org.apache.log4j.examples.Sort.main(Sort.java:64)
 * 467 [main] INFO  org.apache.log4j.examples.Sort - Exiting main method.
 * </pre>
 * 
 * <p>
 * The first field is the number of milliseconds elapsed since the start of the
 * program. The second field is the thread outputting the log statement. The
 * third field is the level, the fourth field is the category to which the
 * statement belongs.
 * 
 * <p>
 * The fifth field (just before the '-') is the nested diagnostic context. Note
 * the nested diagnostic context may be empty as in the first two statements.
 * The text after the '-' is the message of the statement.
 * 
 * <p>
 * <b>WARNING</b> Do not use the same TTCCLayout instance from within different
 * appenders. The TTCCLayout is not thread safe when used in his way. However,
 * it is perfectly safe to use a TTCCLayout instance from just one appender.
 * 
 * <p>
 * {@link PatternLayout} offers a much more flexible alternative.
 * 
 * @author Ceki G&uuml;lc&uuml;
 * @author <A HREF="mailto:heinz.richter@ecmwf.int">Heinz Richter</a>
 */
public class TTCCLayout extends DateLayout {

	// Internal representation of options
	private boolean threadPrinting = true;
	private boolean categoryPrefixing = true;
	private boolean contextPrinting = true;

	protected final StringBuffer buf = new StringBuffer(256);

	/**
	 * Instantiate a TTCCLayout object with
	 * {@link org.apache.log4j.helpers.RelativeTimeDateFormat} as the date
	 * formatter in the local time zone.
	 * 
	 * @since 0.7.5
	 */
	public TTCCLayout() {
		this.setDateFormat(RELATIVE_TIME_DATE_FORMAT, null);
	}

	/**
	 * Instantiate a TTCCLayout object using the local time zone. The DateFormat
	 * used will depend on the <code>dateFormatType</code>.
	 * 
	 * <p>
	 * This constructor just calls the {@link DateLayout#setDateFormat} method.
	 */
	public TTCCLayout(String dateFormatType) {
		this.setDateFormat(dateFormatType);
	}

	/**
	 * The <b>ThreadPrinting</b> option specifies whether the name of the
	 * current thread is part of log output or not. This is true by default.
	 */
	public void setThreadPrinting(boolean threadPrinting) {
		this.threadPrinting = threadPrinting;
	}

	/**
	 * Returns value of the <b>ThreadPrinting</b> option.
	 */
	public boolean getThreadPrinting() {
		return threadPrinting;
	}

	/**
	 * The <b>CategoryPrefixing</b> option specifies whether {@link Category}
	 * name is part of log output or not. This is true by default.
	 */
	public void setCategoryPrefixing(boolean categoryPrefixing) {
		this.categoryPrefixing = categoryPrefixing;
	}

	/**
	 * Returns value of the <b>CategoryPrefixing</b> option.
	 */
	public boolean getCategoryPrefixing() {
		return categoryPrefixing;
	}

	/**
	 * The <b>ContextPrinting</b> option specifies log output will include the
	 * nested context information belonging to the current thread. This is true
	 * by default.
	 */
	public void setContextPrinting(boolean contextPrinting) {
		this.contextPrinting = contextPrinting;
	}

	/**
	 * Returns value of the <b>ContextPrinting</b> option.
	 */
	public boolean getContextPrinting() {
		return contextPrinting;
	}

	/**
	 * In addition to the level of the statement and message, the returned byte
	 * array includes time, thread, category and {@link NDC} information.
	 * 
	 * <p>
	 * Time, thread, category and diagnostic context are printed depending on
	 * options.
	 * 
	 * @param event
	 *            The event to format
	 */
	public String format(LoggingEvent event) {

		// Reset buf
		buf.setLength(0);

		dateFormat(buf, event);

		if (this.threadPrinting) {
			buf.append('[');
			buf.append(event.getThreadName());
			buf.append("] ");
		}
		buf.append(event.getLevel().toString());
		buf.append(' ');

		if (this.categoryPrefixing) {
			buf.append(event.getLoggerName());
			buf.append(' ');
		}

		if (this.contextPrinting) {
			String ndc = event.getNDC();

			if (ndc != null) {
				buf.append(ndc);
				buf.append(' ');
			}
		}
		buf.append("- ");
		buf.append(event.getRenderedMessage());
		buf.append(LINE_SEP);
		return buf.toString();
	}

	/**
	 * The TTCCLayout does not handle the throwable contained within
	 * {@link LoggingEvent LoggingEvents}. Thus, it returns <code>true</code>.
	 * 
	 * @since version 0.8.4
	 */
	public boolean ignoresThrowable() {
		return true;
	}
}
